There are probably more books about leading and managing teams than there are teams in the world. There are new theories daily about how to build a super team. There are self-help books about how to be a great team player. There even books about how to spell team.
I haven't seen too many good books about how to measure the quality of a team. Do they win more awards? Are they more productive? Do they give each other more high fives? Most of the measures seem contrived and derivative.
I think the best teams are the ones that surprise you. Not because they're underdogs. No, the best teams are the ones that get better even after you thought they were already really darn good. We are facing budget cuts at our institution. Never a pleasant process, but sometimes necessary. Normally this activity brings out the worst in people.
In planning for these cuts, I asked my leadership team to come back with budget reduction suggestions for each of their own departments. The surprise: they each did the best they could without regard for whether they were absorbing a disproportionate amount of the change. Instead of being territorial or turf-protecting they worked together. No one bickered and everyone supported each other despite the difficult nature of the process.
That's the sign of a real team.